Automatic shut-off valve for power tool

ABSTRACT

A fluid-actuated shut-off valve for a fluid-powered tool such as a wrench including a spool valve urged to open position by a spring and having respective valve-operating surfaces subject to both inlet and exhaust pressures in the tool. The valve operating surfaces and spring are arranged so the valve is thrown to its closed position by a combination of the rise in inlet pressure and the drop in exhaust pressure as the tool motor slows down and stalls under load.

nited States Patent Qatterield et al. [45] Apr. 18,1972

s4] AUTOMATIC SHUT-OFF VALVE FOR 3,373,824 3/1968 Whitehouse ..173/12 POWER TOOL 3,493,056 2/1970 Boeger et al ..173/12 3,505,928 4/1970 Whitehouse ..173/12 x [72] inventors: Robert J. Catterfeld, Sayre, Pa.; David W.

Tibbott, Phillipsburg, NJ. [73] Assignee: lngersoll-Rand Company, New York, NY. [22] Filed: Sept. 29, 1970 [21] App]. No.: 76,382

Primary Examiner-Emest R. Purser Attorney-Frank S. Troidl and David W. Tibbott [5 7] ABSTRACT A fluid-actuated shut-off valve for a fluid-powered tool such as a wrench including a spool valve urged to open position by [52] US. Cl ..l73/l2, 9l/59, 91/421 3 spring and having respective valve-operating surfaces sub- [51] f" Cl @325!) 23/14 ject to both inlet and exhaust pressures in the tool. The valve [58] held of Search ..l73/l2,9l/59,421 operating Surfaces and spring are arranged so the valve is 56 R f d thrown to its closed position by a combination of the rise in l 1 e erences inlet pressure and the drop in exhaust pressure as the tool UNITED STATES PATENTS motor SlOWS down and stalls under load.

1,414,222 4/1922 Slater ..l73/12 X 9 Claims, 3 Drawing Figures a e a 3 9 29 2 I8 5 |4 I I3 I I6 PATENTEUAPR 18 m2 3, 656, 560

FIG. 2

IN'VENTORS ROBERT J. CATTERFELD DAV/D w. r/aaorr BY 3%. \NTT'W ATTORNEY AUTOMATIC SHUT-OFF VALVE FOR POWER TOOL BACKGROUND OF THE INVENTION This invention relates to power tools and more particularly to a fluid-actuated shut-off valve for a fluid-powered tool such as a wrench.

U.S. Pat. No. 3,373,824, issued Mar. 19, 1968 to H. L. Whitehouse discloses a prior art fluid-actuated shut-off valve for a fluid-powered tool. This valve uses a restriction in the fluid inlet passageway of the tool to increase the range of fluid pressure available to actuate the valve. A restriction is undesirable because it reduces the power of the tool.

SUMMARY OF THE INVENTION A principal object of this invention is to provide a novel fluid-actuated valve mechanism of the foregoing type which substantially eliminates or minimizes the disadvantages of the prior art.

Other important objects of this invention are: to provide a novel shut-off valve actuated by fluid and responsive to the torque load on a tool; to provide a shut-off valve that operates without a restriction in the fluid inlet passage of the tool; and

to provide a tool shut-off valve of a simplified and economical construction which does not reduce the power of a tool.

In general, the foregoing objects are attained in a tool construction including a fluid motor, a fluid inlet passageway and a fluid exhaust passageway, a fluid-operated valve located in the inlet passageway and movable between alternate positions including an open position allowing motive fluid to flow to the motor and a closed position preventing motive fluid from flowing to the motor, spring means urging the valve to its open position, first valve-operating means subject to pressure in the inlet passageway and urging the valve to its closed position, second valve-operating means subject to pressure in the exhaust passageway and urging the valve to its open position with the spring means, said first and second valve-operating means being arranged so that the valve will move to its closed position in response to the drop in fluid pressure in said exhaust passageway when the motor slows down and stalls under a load.

BRIEF DESCRIPTION OF THE DRAWING The invention is described in connection with the accompanying drawing wherein:

FIG. 1 is an elevational view with portions shown in section of a power tool containing the shut-off valve of this invention and showing the valve in its open position;

FIG. 2 is a fragmentary view of FIG. 1 showing the valve spool in elevation and in the closed position; and

FIG. 3 is an enlarged section taken on line 3-3 in FIG. 1.

DESCRIPTION OF THE PREFERRED EMBODIMENT FIG. 1 shows the rear portion of a power wrench casing 1. The casing 1 includes a hose fitting 2 at its rear end adapted to connect to an air hose 3 and opening into a supply or inlet passageway 4. The inlet passageway 4 contains a conventional lever-type throttle valve 5 operated by a throttle lever 6 engaging a plunger 7 connected to the valve 5. The throttle valve 5 is urged shut by a spring 8.

The casing 1 contains a conventional vane-type rotary motor 10 including a rotor 11 mounted in a rear bearing 12 and rotating in a fixed cylinder 13. The rotor 11 also engages a rear end plate 14. The motor includes an inlet 15 connected to the inlet passageway 4 and an exhaust passageway 16.

A novel shut-off valve mechanism is mounted in the casing l in the inlet passageway 4 intermediate the throttle valve 5 and the motor 10. This valve mechanism includes a closed-end housing or sleeve 18 mounted in a corresponding opening provided in the casing 1 and extending across the inlet passageway 4. The valve sleeve 18 is locked in place in the casing l by a roll pin 19. The sleeve 18 contains a cylindrical bore 20 slidably containing a spool valve 21 and having respective inlet and outlet ports 22 and 23 communicating with the passageway 4.

The spool valve 21 is shaped and arranged so that it opens the passageway 4 when in the left position as shown in FIG. 1 and blocks the passageway 4 when in the right position shown in FIG. 2. The left end 24 of the valve 21 contains a cavity which cooperates with the closed end 25 of the valve sleeve 18 to form a chamber 26. A short passage 27 extends from the passageway 4 on the supply side of the valve 21 to a port opening into the valve bore 20 a short distance from the sleeve end 25 where it is covered by the valve 21 in its openposition, as shown in FIG. 1. A clearance is provided between the valve 21 and its bore 20 sufficient for fluid pressure to flow into the chamber 26 from the passage 27 in a restricted manner. The purpose of this restriction will be further explained later: Fluid pressure in the chamber 26 urges the valve 21 toward its closed position.

The right end 29 of the valve 21 contains a cavity which cooperates with a plug 30 threaded into the casing 1 to form a chamber 31 and a spring 32 is disposed in the chamber 31 between the plug 30 and the valve 21 to urge the valve 21 toward its open position. The plug 30 is adjustable to vary the load on the spring 32. In addition, a conduit 33 interconnects the chamber 31 with the exhaust passageway 16 whereby fluid pressure from the exhaust in the chamber 31 urges the valve 21 toward its open position.

A signaling means is incorporated in the valve mechanism for detecting whether the valve 21 is open or closed. The valve 21 contains an annular groove 36 on its periphery adjacent its right end 29 and two passages open into the groove 36 when the valve 21 is open. These are a vent passage 37 and a signal passage 38. The vent passage 37 is located closer to the chamber 31 than the signal passage 38 and the signal passage 38 is located where it is uncovered when the valve 21 is closed, as shown in FIG. 2, so that air can flow from the inlet 4 to the passage 38, thereby providing a signal that the valve 21 is closed. When the valve 21 is open, the vent passage 37 vents any pressure in the signal passage 38. The signal passage 38 can be connected to various devices for detecting, signalling or recording that the shut-off valve has closed to stop the power wrench.

OPERATION In describing the operation of the shut-off valve, we assume that, at the start, the throttle valve is closed, air pressure is in the supply hose 3, the shut-off valve 21 is in its open position as shown in FIG. 1 and the motor 11 is not operating.

The opening of the throttle valve 5 will allow air pressure to quickly start the motor 11. We will assume that the tool is a power wrench, such as an angle wrench, driving a nut as the motor starts. The pressure will rise in the exhaust passageway 16 and in the chamber 31 to urge the valve 21 toward the open position. Also, pressure will flow into the chamber 26 from the inlet passageway 4 to urge the valve 21 toward its closed position. The flow of pressure into the chamber 26 is restricted so that pressure in the chamber 26 cannot rise to full pressure before the exhaust pressure builds up in the chamber 31. While the motor operates, the pressure in the inlet passageway 4 is substantially less than supply pressure due to the motor 11 using a large volume of air. Also, the exhaust pressure in the exhaust passageway 16 is relatively high due to the flow of large air volumes through the motor 11.

As the nut driven by the wrench is tightened, the torque load on the motor rises and eventually stalls. As it slows down and comes to a stop, its consumption of air is reduced causing the air pressure to rise in the inlet passageway and in the valveoperating chamber 26. Also, as the air flow through the motor is reduced the exhaust pressure in the valve-operating chamber 31 is reduced.

Eventually, the diiferential forces on the valve spool 21 are shifted to move the valve toward its closed position. As the valve 21 begins closing and throttling the air flowing through the valve, the pressure in the inlet passageway 4 rises further to further increase the force trying to close the valve 21. As the valve 21 approaches its closed position, as shown in FIG. 2, it uncovers the short passage 27 to allow the air to flow freely from the inlet passageway 4 into the chamber 26. 5

The valve 21 will remain in its closed position as shown in While only a single embodiment of the invention is illustrated and described in detail, this invention is not limited merely to this embodiment, but contemplates other embodiments and variations which utilize the concepts and teachings of this invention.

We claim:

1. A fluid driven power tool including:

a casing containing a motor, an inlet passageway for feeding motive fluid to said motor and an exhaust passageway for exhausting fluid from said motor;

a fluid-actuated valve located in said inlet passageway and movable between alternate positions including an open position allowing motive fluid to flow to said motor and a closed position preventing motive fluid from flowing to said motor;

first valve-operating means urging said valve to its closed position;

second valve-operating means communicating with said exhaust passageway and operative, when subject to fluid pressure, to urge said valve to its open position against the force of said first valve-operating means; and

said first and second valve-operating means being arranged so that said valve will move to its closed position in response to the drop in fluid pressure in said exhaust passageway when said motor slows down.

2. A fluid driven power tool including:

a casing containing a motor, an inlet passageway for feeding motive fluid to said motor and an exhaust passageway for exhausting fluid from said motor;

a fluid-actuated valve located in said inlet passageway and movable between alternate positions including an open position allowing motive fluid to flow to said motor and a closed position preventing motive fluid from flowing to said motor;

spring means in said casing urging said valve to said open position; first valve-operating means communicating with said inlet passageway and operative, when subject to fluid pressure to urge said valve to its closed position against the force of said spring means;

second valve-operating means communicating with said exhaust passageway and operative, when subject to fluid pressure, to urge said valve to its open position against the force of said first valve-operating means; and

said spring means, first and second valve-operating means being arranged so that said valve will move to its closed position in response to the drop in fluid pressure in said exhaust passageway when said motor slows down.

3. The power tool ofclaim 2 wherein:

said valve is a spool valve reciprocating in a bore provided in said casing; and

said first valve-operating means includes a first chamber formed in part by one end of said valve, pressure in said first chamber being operative to urge said valve toward a closed position.

4. The power tool of claim 3 wherein:

said first chamber includes a cavity provided in said one end of said valve.

5. The power tool of claim 4 wherein:

said first chamber communicates with said inlet passageway by a restricted passage which reduces the speed in which pressure can charge in said first chamber. 6. he power tool 0 claim 5 wherein:

said restricted passage includes a port which is substantially closed by said valve when in its fully open position and open when said valve is in its closed position, the clearance between said valve and its bore being enough to allow pressure to leak into said first chamber from said port at a controlled rate.

7. The power tool of claim 3 wherein:

said second valve-operating means is a second chamber formed in part by the other end of said valve, pressure in said second chamber being operative to urge said valve towards its open position.

8. The power tool ofclaim 7 wherein:

said second chamber includes a cavity provided in said other end of said valve spool.

9. The power tool of claim 8 wherein:

said spring is located in said second chamber; and

means is in said casing for adjusting the tension on said spring. 

1. A fluid driven power tool including: a casing containing a motor, an inlet passageway for feeding motive fluid to said motor and an exhaust passageway for exhausting fluid from said motor; a fluid-actuated valve located in said inlet passageway and movable between alternate positions including an open position allowing motive fluid to flow to said motor and a closed position preventing motive fluid from flowing to said motor; first valve-operating means urging said valve to its closed position; second valve-operating means communicating with said exhaust passageway and operative, when subject to fluid pressure, to urge said valve to its open position against the force of said first valve-operating means; and said first and second valve-operating means being arranged so that said valve will move to its closed position in response to the drop in fluid pressure in said exhaust passageway when said motor slows down.
 2. A fluid driven power tool including: a casing containing a motor, an inlet passageway for feeding motive fluid to said motor and an exhaust passageway for exhausting fluid from said motor; a fluid-actuated valve located in said inlet passageway and movable between alternate positions including an open position allowing motive fluid to flow to said motor and a closed position preventing motive fluid from flowing to said motor; spring means in said casing urging said valve to said open position; first valve-operating means communicating with said inlet passageway and operative, when subject to fluid pressure to urge said valve to its closed position against the force of said spring means; second valve-operating means communicating with said exhaust passageway and operative, when subject to fluid pressure, to urge said valve to its open position against the force of said first valve-operating means; and said spring means, first and second valve-operating means being arranged so that said valve will move to its closeD position in response to the drop in fluid pressure in said exhaust passageway when said motor slows down.
 3. The power tool of claim 2 wherein: said valve is a spool valve reciprocating in a bore provided in said casing; and said first valve-operating means includes a first chamber formed in part by one end of said valve, pressure in said first chamber being operative to urge said valve toward a closed position.
 4. The power tool of claim 3 wherein: said first chamber includes a cavity provided in said one end of said valve.
 5. The power tool of claim 4 wherein: said first chamber communicates with said inlet passageway by a restricted passage which reduces the speed in which pressure can change in said first chamber.
 6. The power tool of claim 5 wherein: said restricted passage includes a port which is substantially closed by said valve when in its fully open position and open when said valve is in its closed position, the clearance between said valve and its bore being enough to allow pressure to leak into said first chamber from said port at a controlled rate.
 7. The power tool of claim 3 wherein: said second valve-operating means is a second chamber formed in part by the other end of said valve, pressure in said second chamber being operative to urge said valve towards its open position.
 8. The power tool of claim 7 wherein: said second chamber includes a cavity provided in said other end of said valve spool.
 9. The power tool of claim 8 wherein: said spring is located in said second chamber; and means is in said casing for adjusting the tension on said spring. 